Sealant materials for toner cartridges

ABSTRACT

A silicone copolymer for use in an electrophotographic process is disclosed. This composition includes a specifically-defined heat-stable silicone oil-silicone wax copolymer. The copolymer has a melting point such that it is liquid on the hot fuser roll, but solidifies at room temperature on the printed page. A random silicone copolymer, in the form of a paste or pliable caulk, which is useful for sealing leaks in toner cartridges is also disclosed. Finally, the method for preparing these copolymers is disclosed.

RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.08/937,368, now U.S. Pat. No. 5,952,442; Dowlen et al., filed Sep. 25,1997, and a continuation-in-part of U.S. patent application Ser. No.08/855,373, now U.S. Pat. No. 5,880,224; Dowlen et al., filed May 13,1997.

TECHNICAL FIELD

The present invention relates to electrophotographic printing andspecifically to a sealant used in toner cartridges.

BACKGROUND OF THE INVENTION

In the process of electrophotography, the light image of an original tobe copied is typically recorded in the form of a latent electrostaticimage upon a photosensitive member with a subsequent rendering of thatlatent image visible by the application of electroscopic markingparticles, commonly referred to as toner. The visual toner image can beeither fixed directly upon the photosensitive member or transferred fromthe member to another support, such as a sheet of paper, with subsequentaffixing of the image thereto.

In order to fix or fuse electroscopic toner material onto a supportmember permanently by heat, it is necessary to elevate the temperatureof the toner material to a point at which the constituents of the tonerbecome tacky. This action causes the toner to flow to some extent intothe fibers or pores of the support member. Thereafter, as the tonermaterial cools, solidification occurs causing the toner material tobecome bonded firmly to the support member. In electrophotography, theuse of thermal energy for fixing toner images onto a support member isold and well known.

One approach to thermal fusing of electroscopic toner images has been topass the support with the toner images thereon between a pair of opposedroller members, at least one of which is internally heated. Duringoperation of this type of fusing system, the support member to which thetoner images are electrostatically adhered is moved through the nipformed between the rolls with the toner image contacting the fuser roll,thereby heating the toner image within the nip. By controlling the heattransfer to the toner, virtually no offset of the toner particles fromthe copy sheet to the fuser roll is experienced under normal conditions.This is because the heat applied to the surface of the roller isinsufficient to raise the temperature of the surface of the roller abovethe "hot offset" temperature of the toner at which temperature the tonerparticles in the image areas of the toner liquify and cause a splittingaction in the molten toner resulting in "hot offset." Splitting occurswhen the cohesive forces holding the viscous toner mass together is lessthan the adhesive forces tending to offset it to a contacting surface,such as a fuser roll.

Occasionally, however, toner particles will be offset to the fuser rollby an insufficient application of heat to the surface thereof (i.e.,"cold" offsetting). This is generally caused by imperfections in theproperties of the surface of the roll, or by the toner particles notadhering to the copy sheet as a result of insufficient adhesion forces.In such a case, toner particles may be transferred to the surface of thefuser roll with subsequent transfer to the back-up roll during periodsof time when no copy paper is in the nip.

Moreover, toner particles can be picked up by the fuser and/or back-uproll during fusing of duplex copies or simply from the surroundings ofthe reproducing apparatus. The presence of such wayward toner particlescan result in poor copy quality.

Most fusers of the type described above employ some method of applying arelease fluid to the hot roll. Because of their inherent temperatureresistance and release properties, silicone oils are typically used toprevent toner from adhering to the surface of the fuser roll and therebydegrading image quality and contaminating the fuser surface. Thesilicone oil also extends the life of the fuser rollers by providingsome measure of lubrication to reduce the wear caused by the cumulativeaction of tens of thousands of pages passing through the pressure nip ofthe fuser. In order to assure the positive effects of the release fluid,a minimum amount of oil (typically 10-100 micrograms per page) isrequired.

Since the oil used as a release agent is partially carried away by thepaper passing through the fuser system, it is necessary to ensure thatthe amount of oil dispensed is not so much that objectionable printquality defects are seen. In extreme cases, the surface of the imagedpage can become visibly wet or glossy with oil. In cases of duplexprinting (i.e., printing on both sides of the page), a more subtleeffect is seen. In that instance, oil is carried back through theprinting process by duplexed pages and the oil on those pages isdeposited on various machine surfaces, including the photoconductor. Ithas been found that minute amounts of oil, invisible to the eye, can beenough to drastically effect the transfer of toner from the developerroll to the photoconductor. Since the development process depends upon ascrubbing action between the toned developer and the imagedphotoconductor to aid in the transfer of toner from the developer to thephotoconductor, and since the scrubbing action is induced by a mismatchin surface speed between the developer and the photoconductor, theaddition of silicone oil at the interface of the two surfaces reducesthe frictional scrubbing force to a level where transfer of toner can beseverely impaired. Such print quality defects are very apparent in fineresolution printing. In extreme cases, the lack of toner transfer isseen even in 12 point text as light print. Levels of oil exceeding 100micrograms per page can cause severe print defects if the distributionof oil across the page is not uniform. Typical print quality defects arewhite streaks in gray scale, with the streaks parallel to the processdirection in areas of high oil concentration. For this reason, the upperlimit of oil metering is about 100 micrograms per page.

A typical lubricant metering scheme employed in low-cost desk topprinters involves saturating a felt pad constructed of temperatureresistant material (such as DuPont's NOMEX Fiber) with silicone oil of aviscosity such that, when combined with the fiber size and density ofthe felt, the rate of flow out of the felt can be controlled withinreasonable limits. Typical construction of a wiper pad includesapplication of an amount of silicone oil (e.g., 7-8 grams) of viscosityabout 30,000 cst (at room temperature) to a precut piece of felt (e.g.,fiber diameter 9 microns, felt density≈55 oz./yd².), and baking thefelt/oil combination at a high temperature to allow the oil to soak intothe felt. Before high resolution printing (1200 DPI) and duplexprinting, such a scheme was an excellent metering system, controllingoil flow within a range of 50-500 micrograms per page, with reasonableflow uniformity and no image defects. When this metering scheme is usedwith 1200 DPI and duplex printing, however, the previously acceptablenon-uniform distribution of oil produces oil concentrations in someareas that are high enough to result in the above-described printdefects.

Another requirement of the oil application system is that the amount ofoil dispensed must be consistent during the life of the applicator(typically about 14,000 pages). As previously mentioned, failure tomaintain adequate oil flow causes toner to adhere to the fuser andreduces the life of the fuser. Also, low flow allows toner to becollected on the felt applicator; when enough toner accumulates, a massof toner breaks free and adheres to the page causing another printquality defect called "wiper dump." The felt applicator is a gravityfeed system. This means that oil flows out of the felt at a constantrate for a given temperature. Silicone oil continuously flows out of thewiper even if the printer is not printing and is at standby. Thus, ifthe printer is at standby for a sufficient amount of time, the firstpage printed will receive an abnormally large amount of silicone oil andshow duplex streaks.

In summary, for optimum performance the release agent oil applicationsystem must meet the following requirements:

Sufficient and consistent oil flow over the life of the system toprevent adherence of toner to the fuser roll. This extends fuser andprevents wiper dumps. Minimum flow rate of 10 micrograms per page.

A maximum flow rate of 100 micrograms per page and uniform flow toprevent image defects when printing high resolution images at 1200 DPIand in duplex mode.

U.S. Pat. No. 4,185,140, Strella, et al., issued Jan. 22, 1980,describes polymeric release agents for use on hot fuser rolls in anelectrophotographic duplication process. The polymer materials utilizedmust include functional groups such as carboxy, hydroxy, isocyanate,thioether or mercapto groups. These materials are said to form athermally stable release layer on the fuser roll which has excellenttoner release properties. It is taught that the polymer material may besolid at room temperature, as long as it is a liquid at the temperatureof the fuser, The materials disclosed as release agents are not siliconeoils or waxes.

The present invention defines release agents which, when used on a hotfuser roll in an electrophotographic process, eliminate the problemsdescribed above. The material is liquid on the fusing surface andsolidifies on the print medium when cool. It serves as an effectiverelease agent (i.e., it prevents toner from adhering to the surface ofthe fuser roll and lubricates the fuser roll) and prevents print qualitydefects which result from the presence of oil on the paper, particularlyduring duplex printing.

Print quality issues can also arise as the result of toner leaks fromthe print cartridge. The toner cartridge is a replaceable supply used inprinters and photocopiers. Its function is to hold a supply of the tonerin a reservoir and then transfer the toner from that reservoir onto thedeveloper roll, where it is present as a monolayer. The toner is thentransferred onto the photoconductor in a pattern corresponding to theimage to be printed, based on a charge distribution created on thephotoconductor surface. Toner cartridges are well-known in theelectrophotographic art and are, for example, described in U.S. patentapplication Ser. No. 08/770,330, Coffey, et al., filed Dec. 20, 1996,now U.S. Pat. No. 5,802,432, incorporated herein by reference.

Careful transfer of the toner is critical to obtaining good printedimages. Leaking toner will result in poor image quality, as well assoiling of the user's hands, clothing and office. A particularlytroublesome spot on the cartridge, where toner leakage is likely tooccur, is at the ends of the developer roll. In fact, toner cartridgesfrequently utilize specific seals, such as the J-seal, to prevent tonerleakage at the ends of the developer roll. Despite that, some leakagestill occurs due to variability in cartridge parts and assembly. Aliquid or grease seal could be considered for use in the cartridge, forexample at the ends of the developer roll. However, that could causeproblems since such materials tend to migrate and migration of thesealant into the print area call cause contamination of the developerroll, the photoconductor and the charge roll, thereby causing printdefects.

Therefore, it is a further object of the present invention to provide asilicone copolymer which, when formulated to have a paste or caulk-likeconsistency, serves as an effective sealant for use on toner cartridges,which does not migrate, is easy to apply and can be spread as a thinlayer.

SUMMARY OF THE INVENTION

The present invention relates to a silicone copolymer, particularly arandom silicone copolymer, which may be used as a sealant in a tonercartridge, having structural units of the formulae: ##STR1## wherein (i)each R is independently a C₁ -C₆ alkyl, (ii) each R¹ is independentlyselected from the group consisting of a C₂ -C₁₄ alkyl and C₁₅ -C₆₀alkyl, with the proviso that from about 70% to about 100% of all R¹groups are C₁₅ -C₆₀ alkyl, and (iii) x preferably represents from atleast about 98.5 to about 99.5 mole percent, and y preferably representsfrom about 0.5 to less than about 1.5 mole percent of the siliconecopolymer, based on total moles of the silicone copolymer. Preferredcopolymers are terminated by groups having the formulae: ##STR2##wherein R² is C₁ -C₆ alkyl or aryl. Preferred copolymers have amolecular weight (weight average) of from about 10,000 to about1,000,000, more preferably from about 80,000 to about 250,000. Thecopolymers are in the form of a paste or caulk and have a viscosity offrom about 3,000 to about 7,000 centipoise at about 93° C. Tonercartridges which utilize these copolymers as a sealant are also claimed.

DETAILED DESCRIPTION OF THE INVENTION

The key element of the present invention is a silicone copolymer,especially a random silicone copolymer, having components comprisingalkyl methyl siloxane and dimethylsiloxane. This polymer has meltingpoint and viscosity characteristics such that it is liquid on the heatedfusing roll surface in an electrophotographic process, but solidifies asit cools on the print surface (i.e., the paper). The precise meltingpoint and viscosity characteristics can be selected and optimized basedon the particular dispenser and fuser system to be used.

Organosilicone waxes are well known and are used extensively in thecosmetics industry. However, none of these commercial waxes has theproperties which render it useful as a release agent on a fuser roll. Asilicone wax must meet the following requirements to be useful as arelease agent in a laser printer:

High thermal stability. The wax can have no odor throughout the life ofthe composition and should not appreciably change physical properties,such as viscosity.

The wax must have a melt viscosity of from about 2,000 to about 10,000centipoise, preferably from about 3,000 to about 7,000 centipoise, mostpreferably about 3,500 cps, at about 93° C. This matches the siliconeoil viscosity at fusing temperature and allows the wax to be directlysubstituted into the felt pad dispensing system.

The wax must have a melting point between about 45° C. and about 80° C.If the melting point is below about 45° C., the wax will not solidifywhen the printer is running at full speed and the cartridge is hot;thus, duplex streaks can occur. If the melting point is above 80° C.,the wax will solidify on the backup roll when printing heavy media andcollect paper dust and toner which could cause the media to wrap thebackup roll.

At standard flow rates, the wax must not produce streaks ontransparencies. This is accomplished by having a flow rate of less thanabout 800 micrograms per page.

The copolymer utilized as the release agent in the present inventioncomprises structural units represented by the formulae given below.These copolymers may be block copolymers or random copolymers, althoughrandom copolymers are preferred. ##STR3##

In these formulae, the x portion of the molecule has the properties of asilicone oil, and the y portion of the molecule has the properties of analiphatic hydrocarbon wax. x represents the molar percent of thecopolymer which comprises the silicone oil moieties; x is from about75.0 to about 98.5 mole percent, preferably from about 85.0 to about98.0 mole percent, most preferably about 97 mole percent. y representsthe molar percent of the copolymer which comprises the silicone waxportion; y has a value of from about 1.5 to about 25.0 mole percent,preferably from about 2.0 to about 15.0 mole percent, most preferablyabout 3.0 mole percent. These percentages are based on total moles ofthe silicone copolymer. In preferred polymers, the molar ratio of x:y isfrom about 15:1 to about 70:1, preferably from about 25:1 to about 50:1,more preferably from about 30:1 to about 45:1, and is most preferablyabout 32:1. Each of the R¹ groups is independently selected from C₂ -C₁₄alkyl and C₁₅ -C₆₀ alkyl, with the proviso that from about 70% to about100% (by weight) of all R¹ groups are C₁₅ -C₆₀ alkyl and the remainderof the R¹ groups are C₂ -C₁₄ alkyl (preferably hexyl). Low levels ofhydride (i.e., less than about 10% of the original hydride content) maybe tolerated in R¹. Both of the alkyl components may be halogenated,preferably fluorinated. It is preferred that the major component in R¹be C₃₀ -C₄₅ alkyl, most preferably C₃₆ alkyl. An example of such amaterial is Gulftene 30+, commercially available from Chevron. Each R isindependently selected from C₁ -C₆ alkyl, and is preferably methyl.

Within the ranges of x and y, defined above, the release agentcopolymers may be optimized to have specific desirable characteristicsfor different applications. Thus, a copolymer having x/y equal to about97/3 may be particularly useful when a printer does both transparenciesand duplexing. A copolymer having x/y equal to about 95/5 may beparticularly useful where heavy duplexing is required. In the preferredcopolymers, x/y (molar ratio) is from about 95/5 to about 97/3.

Preferred copolymers are terminated with the following groups ##STR4##wherein each R² is independently selected from C₁ -C₆ alkyl or arylgroups, and is preferably methyl.

The copolymer should have a molecular weight (weight average) of fromabout 10,000 to about 1,000,000, preferably from about 80,000 to about250,000, more preferably from about 80,000 to about 150,000, mostpreferably about 110,000. Importantly, the copolymer must beheat-stable. By "heat-stable" is meant that the copolymer can be held at210° C. for three months with no significant change in color, odor,viscosity or molecular weight.

The release agent composition of the present invention comprises fromabout 50% to about 97%, preferably from about 75% to about 95%, and mostpreferably about 91% of the copolymer component described above. Themelt viscosity of the composition is particularly important because itis one of the major factors in determining the rate at which the releasecomposition is dispensed onto the fusing roll. The viscosity of thepolymer is optimized for the particular dispensing means used.Typically, the melt viscosity of the composition should be from about2,000 to about 10,000 centipoise at about 93° C., preferably from about3,000 to about 7,000 centipoise at about 93° C., and most preferablyabout 3,500 centipoise at about 93° C. The melting point of the releaseagent composition is also critical because it is the melting point thatwill determine whether the composition is actually a liquid on the fuserroll and a solid when cooled on the printed paper. The compositionshould, therefore, have a melting point of from about 45° C. to about80° C., preferably from about 65° C. to about 80° C., and mostpreferably about 72° C.

The melt viscosity of the composition may be adjusted in several ways tomake sure that it falls within the required range and is optimizedwithin that range for the particular electrophotographic deviceinvolved. Two ways to adjust the viscosity is to control the viscosityof the hydride siloxane copolymer by using a chainstopper, or bycontrolling the level of crosslinking of the copolymer while it is beingformed. Those processes will be described below as part of the methodfor manufacturing the copolymer. Another way to adjust the viscosity isto add a viscosity control agent to the composition. When used, theseagents generally comprise from about 0.5% to about 30%, preferably fromabout 10% to about 25%, and most preferably about 20% of thecomposition. The particular agent selected may either be added toincrease the viscosity or decrease the viscosity of the composition.Examples of useful viscosity modifying agents include amorphous (fumed)silica (especially amorphous silica having a hexamethyldisiloxanesurface treatment), silicone oil, and mixtures thereof. The preferredviscosity control agent is silicone oil, 30,000 centistoke. In additionto adjusting the viscosity of the composition, the silicone oil alsoenhances the lubricating ability and adjusts the flow rate of thecomposition.

Since the release agent compositions of the present invention are usedunder a variety of temperature conditions (the high temperatures of thefuser roll as well as ambient room temperature) it is important that thecomposition, and particularly the copolymer, be stable so as toeliminate any odor, decomposition and crosslinking problems which mayoccur. This may be accomplished by adding an antioxidant to thecomposition to provide thermal stability at the fusing temperatures.When used, the antioxidant generally comprises from about 3% to about20%, preferably from about 5% to about 13%, and most preferably about 9%of the composition. Although the antioxidant is important to achievecomposition stability, if it is used at too high levels, undesired "foilstreaks" may be seen on printed copies. Any conventional antioxidant maybe used. Mixtures of antioxidants which operate by differing mechanismsare preferred. Examples of such useful antioxidants include thefollowing classes of materials:

(a) free radical scavengers--such as hindered phenols;

(b) phosphite materials; and

(c) hydroperoxide decomposers--such as thiodipropionate materials; and

(d) mixtures of the foregoing materials.

A particularly preferred mixture of antioxidants includes Irganox 1010(a hindered phenol type antioxidant, commercially available from CibaGeigy), Cyanox STDP (distearylthiodipropionate, commercially availablefrom Cytek Industries), and Mark 2112 (a high temperature phosphiteantioxidant, commercially available from Witco Corp.).

In another aspect of the present invention, an organosiloxane material,particularly a silicone copolymer having the following structural unitsmay be used as a sealant, for example, on toner cartridges: ##STR5##

These copolymers may be block copolymers or random copolymers, althoughrandom copolymers are preferred. In these formulae, x can be from 0 toabout 99.5 mole percent, although it preferably is from greater thanabout 98.5 to about 99.5, more preferably from about 98.8 to about 99.5,more preferably from about 99.0 to about 99.2, and most preferably about99.0, mole percent of the copolymer. y can be from about 0.5 to about100 mole percent of the copolymer, although it preferably is from about0.5 to less than about 1.5, more preferably from about 0.5 to about 1.2,more preferably from about 0.8 to about 1.0, and most preferably about1.0 mole percent of the copolymer. Each of the R¹ groups isindependently selected from C₂ -C₁₄ alkyl and C₁₅ -C₆₀ alkyl with theproviso that from about 70% to about 100% (by weight) of the R¹ groupsare C₁₅ -C₆₀ alkyl group and the remainder of R¹ groups are C₂ -C₁₄alkyl (preferably hexyl) groups. Low levels of hydride (i.e., less thanabout 10% of the original hydride content) may be tolerated in R¹. Bothof the alkyl components may be halogenated, preferably fluorinated. Itis preferred that the major component in R¹ be C₃₀ -C₄₅ alkyl, mostpreferably C₃₆ alkyl. An example of such a material is Gulftene 30+,commercially available from Chevron. Each R is independently selectedfrom C₁ -C₆ alkyl, and is preferably methyl. The copolymer should alsopreferably be heat-stable.

Preferred polymers are terminated with the following groups ##STR6##wherein each R² is independently selected from C₁ -C₆ alkyl or arylgroups, and is preferably methyl.

The molecular weight (weight average) of the copolymer is from about10,000 to about 1,000,000 preferably from about 80,000 to about 250,000,more preferably from about 80,000 to about 150,000, most preferablyabout 110,000. Rather than a wax, which is the consistency of thepreviously described copolymer, the copolymer useful as a sealant hasthe consistency of a paste or a pliable caulk. The sealant copolymer hasa viscosity of from about 3,000 to about 7,000 centipoise at about 93°C. For each particular sealant copolymer, it is within the knowledge ofone of ordinary skill in the art to vary the values of x and y and thecopolymer's molecular weight to achieve the desired viscosity. Thecopolymer may be used in combination with antioxidants, as describedabove.

This silicone copolymer material is useful for sealing leaks, forexample in a toner cartridge, especially at the ends of the developerroll. The structure of such cartridges is well-known in the art as, forexample, disclosed in U.S. patent application Ser. No. 08/770,330,Coffey, et al., filed Dec. 20, 1996, now U.S. Pat. No. 5,802,432,incorporated by reference herein. To accomplish this sealant function aneffective amount (from about 5 mg to about 100 mg, preferably about 40mg) is placed on each J-seal extending downward from the upper junctionwith the Mylar lower developer seal to cover the entire junction of thisMylar lower developer seal and the plastic housing side plate. Thedeveloper roll is then installed and turned, wetting the surface of theJ-seal, lower developer roll seal end, and the end surfaces of thedeveloper roll with the copolymer. The copolymer is easy to apply. Thisthin layer of the copolymer acts to effectively seal toner leaks and thecopolymer does not migrate into the print area, in use.

The copolymers used in the present invention may be synthesized by anymethod known in the art. The steps generally will include thecopolymerization of cyclic siloxane (D4) and silicone hydride componentsto form a silicone prepolymer and then grafting the long chain alkenegroup onto that prepolymer.

An example of a reaction which can be used to accomplish this follows:

Step 1 ##STR7##

Step 2 ##STR8##

Step 1 Reaction

In a 1000 ml four-neck round bottom flask equipped with a thermometer,condenser, mechanical stirrer, and a septum, add 209.39 g of D4; 10.45 gof PMHS; 0.95 g of dried bentonite (F-105 at 100C for four hours) and0.333 g of hexamethyl disiloxane (HMDS) (432.9 μL). Fill the reactionflask with nitrogen. Slowly heat the mixture to 90° C. with 500 RPMstirring. Hold at 90° C. for 7 hours. The viscosity of the mixtureshould reach 6000 cps. To remove any unreacted D4, heat the mixtureunder high vacuum at 125° C. To viscosity of the mixture should reach7000 cps. The hydride content of the copolymer is measured by proton NMRand is about 5 mole %.

Step 2 Reaction

Cool the reaction flask from step 1 to room temperature. Then add 129.3g of 61.4 % triacontene (e.g., Gulftene 30+, commercially available fromChevron, a mixture of alkene materials having an alpha-olefin contentgreater than 60%, and an average chain length of about 36) and 400 mltoluene (dried with molecular sievers) and DMS-VO5 (divinyl PDMS) ifneeded, to the reaction flask from step 1. Fill the reaction mixturewith nitrogen. Heat to 75° C., measure infrared spectra (IR) of asolution aliquot to determine the amount of remaining hydride, and add90 μL of PC072 (Platinum, 1,3-diethenyl-1,1,3,3-tetramethyldisiloxanecomplex) (time=0 min.). At 20 minutes add 90 μL of PC072 and measure thehydride content by IR. The ratio of the hydride peak at time t comparedto the size of the peak at time=0 is taken as the hydride content(percent hydride; H%). Continue to add 90 μL every 20 minutes taking IRof the aliquot until H% reaches 25 to 30% from IR (no less than 40 min.addition; no more that 60 min. addition). When the H% reaches 25-30%,add 50 ml of hexene and 90 μL of PC072 (quench time=0 min.). At 30minutes add another 90 μL of PC072. Continue monitoring by IR until theH% is below 10% (normally 1 hour). Extract a small sample for analysis(dry under vacuum separately).

Procedure for Adding Antioxidant

From step 2, add in 30% silicone oil (30000 cp), 10% Cyanox STDP. 2%Irganox 101, 3% Mark 2112 based on the amount of wax (if assumed 338 gwax is produced: 101.6 g Si-oil, 33.8 g STDP, 6.67 g 1010 and 10.14 g2112) heat to 100° C. and stir until mixed (1 hour). Pour into ovendish, dry in explosion-proof oven (˜75° C.) overnight.

The melt viscosity of the copolymer and, therefore, of the release agentcomposition, may be effectively influenced by controlling thecrosslinking of the copolymer while it is being prepared. Crosslinkingagents which may be used for this purpose include divinyl-terminatedpolydimethyl siloxane. This approach is useful when a higher molecularweight copolymer is desired. The result of this procedure is to increasethe copolymer viscosity in a controlled manner making the flow rate ofthe copolymer wax product more controllable.

When a lower molecular weight copolymer is desired, from about 0.1 toabout 0.5 weight percent (preferably about 0.26%) of a chain-stoppermaterial may be added to the step 1 reaction. Effective chain-stoppersinclude any low molecular weight PDMS, such as hexamethyl disiloxane(HMDS). It is preferred that this reaction take place in the presence ofbentonite.

After the step 2 reaction is completed, it is preferred that thereaction be quenched with a volatile low molecular weight 1-alkene(e.g., C₂ -C₁₄ alkenes), such as 1-hexene. This quenching step replacesany hydrides in the material synthesized with the short alkyl chain toprevent further reaction of any hydrides, such as self-crosslinking. Upto about 30% of the y groups on the copolymer can be sosubstituted-greater amounts can adversely affect viscosity of thematerial.

It has surprisingly been found that when the effective amount ofreaction catalyst (see step 2, above) is added stepwise to the reactionmixture over the course of the reaction, the reaction goes furthertoward completion than if the catalyst had all been added at one time.Therefore, the present invention encompasses the reaction for making arandom silicone copolymer comprising reaction of a C₁₅ -C₆₀ 1-alkene(preferably a C₃₀ -C₄₅ alkene, most preferably C₃₆ alkene) with amethylhydrosiloxane-containing prepolymer (preferably a PDMS-containingprepolymer, more preferably a PDMS-co-PMHS prepolymer, most preferablyone having a PDMS:PMHS molar ratio of about 32:1) in the presence of aGroup VIII b catalyst material, for example, those selected fromplatinum, palladium, and mixtures thereof (preferably platinum) whereinthe catalyst is added to the reaction mixture in portions throughout thecourse of the reaction, until the reaction is complete. Since the1-alkene is generally present in the reaction as a mixture of alkenes,it is preferred that it have a high purity (e.g., it should contain atleast about 60% by weight of the desired alkene). It is also preferredthat the reaction should be quenched with a short chain (C₂ -C₁₄)1-alkene (preferably n-hexene) when the reaction is complete. By"effective amount" of catalyst is meant the total amount of catalystnecessary to catalyze the reaction. The precise amount will depend onthe identity of the specific catalyst and reactants used and will bewithin the knowledge of one skilled in the art.

A typical fuser assembly for use in an electrophotographic processcomprises a heated roll structure including a hollow cylinder or corehaving a suitable heating element disposed in the hollow portion thereofwhich is coextensive with the cylinder. The heating element may compriseany suitable type of heater for elevating the surface temperature of thecylinder to operational temperatures which are generally from about 250°F. to about 400° F. (from about 115° C. to about 204° C.) and, forexample, may be a quartz lamp. The cylinder may be fabricated from anysuitable material capable of accomplishing the objects of the invention,that is, a material which not only will transfer heat to the surface toprovide the temperature required for fusing toner particles, but also amaterial having a surface which is capable of interacting with therelease compositions of the present invention to form an interfacial orbarrier layer to toner between the release layer and the surface of thebarrier fuser member to prevent toner particles from contacting thefuser surface.

Typical fuser member materials include anodized aluminum and alloysthereof, steel, stainless steel, nickel and alloys thereof,nickel-plated copper, copper, glass, zinc, cadmium, and the like, aswell as various combinations of the above materials. The cylinder mayalso be fabricated from ally suitable material which is nonreactive withthe release agent compositions as long as the surface of the cylinder iscoated with a material capable of accomplishing the objects of thepresent invention. Surface temperature of the fuser member may becontrolled by means known to those skilled in the art, for example, bymeans described in U.S. Pat. No. 3,327,096.

In general, the fuser assembly further comprises a backup member, suchas a roll or belt structure which cooperates with the fuser rollstructure to form a nip through which a copy paper or substrate passessuch that the toner images thereon contact the fuser roll structure. Thebackup member may comprise any suitable construction, for example, asteel cylinder or a rigid steel core having an elastomeric layerthereon, or it may be a suitable belt material which provides thenecessary contact between the fuser member and the substrate carryingthe developed latent image. The dimensions of the fuser member and thebackup member may be determined by one skilled in the art and generallyare dictated by the requirements of the particular electrophotographicapparatus in which the fuser assembly is employed, the dimensions beingdependent upon the process speed and other parameters of the machine.Means may also be provided for applying a loading force in aconventional manner to the fuser assembly to create nip pressures on theorder of from about 15 to about 150 psi average.

The fuser member treated with the release agent compositions of thepresent invention, said compositions being applied in an amountsufficient to cover the surface with at least a continuous, low surfaceenergy film of the composition to prevent the nonreactive thermoplasticresin toner from contacting the surface of the fuser member and toprovide a surface which releases the thermoplastic resin toner heated bythe fuser member, is also a part of the present invention.

Finally, the present invention encompasses a pad used for dispensing therelease agent of the present invention onto the fuser member. This padcomprises a felt pad constructed from a temperature resistant fiberimpregnated (saturated) with an effective amount (e.g., about 6 to about10 grains) of a release agent composition of the present invention.

The following examples are intended to illustrate the compositions andthe methods of the present invention and are not intended to be limitingthereof.

EXAMPLE 1

A release agent composition of the present invention has the followingcomponents.

    ______________________________________                                                                      Parts                                              (by                                                                          Material wt.)                                                               ______________________________________                                        3 mole percent Methyl-Triacontylsiloxane-97 mole percent                                                    100                                               Dimethylsiloxane Copolymer.sup.1                                              Silicone Oil, 30,000 centistoke 30                                            Cyanox STDP antioxidant (commercially available from 10                       Cytec Industries)                                                             Irganox 1010 antioxidant (commercially available from Ciba 2                  Geigy)                                                                        Mark 2112 antioxidant (commercially available from Witco Corp.)             ______________________________________                                                                      3                                                .sup.1 The copolymer of formula (1) wherein x = 97, y = 3, and R is about     75% C.sub.36 alkyl and about 25% hexyl.                                  

The addition of more antioxidant to the composition increases thermalstability, but also reduces viscosity.

The above composition is made in the following manner: To the copolymermaterial dissolved in toluene, the silicone oil and antioxidants areadded, heated to 100° C. and stirred for about 1 hour. The mixture isthen poured into an oven dish and dried in an explosion-proof oven (˜75°C.) overnight.

This composition, when applied to the fuser roll an electrophotographicdevice, provides excellent release agent properties without streaking orotherwise adversely affecting the quality of the printed pages produced.

EXAMPLE 2

A composition of the present invention is prepared in the followingmanner.

Synthesis of PDMS-co-PMHS Prepolymer

In a flask equipped with a mechanical stirrer and condenser,octamethylcyclotetrasiloxane 110.2 g, polymethylhydrosiloxane (Aldrich17,620-6) 3.1 g, acid leached bentonite (Grade P-20X) 0.32 g, andhexamethyldisiloxane 0.3 g, are added and degassed with Firestone Valveequipment. The mixture is heated to 90° C. for 18 hours, then cooled toroom temperature. After cooling to room temperature, the product isanalyzed by NMR and viscometry. (PDMS:PMHS=97:3 mole percent; viscosityat room temperature equals 4,000-8,000 cst).

Preparing the Crosslinked Siloxane Wax Copolymer

In a flask equipped with a mechanical stirrer and condenser,PDMS-co-PMHS (5,000 cst) 18.5 g, triacontene (66%; average C=36) 6.29 g,and toluene 60 mL, are added and degassed with Firestone Valveequipment. The mixture is heated to 60° C. to melt the triacontene andan aliquot of the mixture is collected and the % hydride is determinedby infrared spectroscopy for the sample. Then 6 μL of platinumdivinyl-terminated tetramethylsiloxane complex (PC072) is added. Afteraddition, the temperature is raised to 70° C. After 15 minutes, anotheraliquot (% H by IR) is taken and at 20 minutes 6 μL of PC072 is added.After 30 minutes, another aliquot (% H by IR) is taken and at 40 minutes6 μL of PCO72 is added. After 50 minutes, another aliquot (% 11 by IR:should be less than 30%) is taken and at 60 minutes, 5 mL of hexene and6 μL of PC072 are added. After 90 minutes, 6 μL of PC072 is added and at120 minutes a final aliquot is taken to assure %H is less than 10%. Allaliquot is collected and dried under vacuum to determine the percent ofthe solid in the product. The final siloxane wax copolymer containsabout 3% alkene and 97% siloxane. [A fluorinated copolymer may beprepared by substituting 10 mL 1H, 1H, 2H-perfluoro-1-hexene in place ofhexene in the above reaction.]

To ensure the thermal stability of the siloxane copolymer wax at fusingtemperature, some other additives are also mixed with the wax beforeusing in the fusing system. The composition comprises the followingcomponents: copolymer wax, described above; a primary antioxidant,Irganox 1010, commercially available from Ciba Geigy: 1.2 parts per 100parts wax; a secondary antioxidant, Cyanox STDP(distearylthiodipropionate, commercially available from CytekIndustries): 6 parts per 100 parts wax; and a high temperature phosphiteantioxidant, Mark 2112 (commercially available from Witco Corporation):1.8 parts per 100 parts wax. These additives are added to the siloxanewax copolymer dissolved in toluene, stirred well and then poured into adish and dried in a flame-proof oven at 80° C. overnight.

8.5 g of the composition is dispensed onto one side of a Nomex (DuPont)felt pad (fiber diameter=9 microns, felt density≈55 oz/yd², length=213mm, width=8 mm, depth=11 mm). The wax and felt are baked at 140° C. for8 hours to ensure the wax is evenly distributed in the felt. Once baked,the side of the felt pad that the wax is initially dispensed upon ispositioned in the wiper housing of an electrophotographic device suchthat this side contacts the fuser hot roll. The fuser hot roll ismaintained at 200° C. This temperature melts the wax all the way throughthe wiper and this allows the wax to flow as a normal lubricant.

The composition, when used on a fuser roller in an electrophotographicprocess, prevents the sticking of toner particles to the fuser roll,lubricates the fuser roll during use, and does not result in streakingor other print quality defects in the printed pages produced.

EXAMPLE 3

A copolymer of the present invention useful as a sealant is synthesizedas follows:

Step 1

In a 1000 mL four-neck round bottom flask equipped with thermometer,condenser, mechanical stirrer, and septum, add 213.05 g of D4, 1.93 g ofPMHS, 0.62 g of dried bentonite (F-20X at 100° C. for four hours), and0.744 g of HMDS (967 μL). Fill the reaction flask with nitrogen. Slowlyheat the mixture to 90° C. with 500 RPM stirring. Hold at 90° C. for 18hours. To remove any unreacted D4, heat the mixture under high vacuum at125° C. The viscosity of the material should reach 5,000 cps. Thecontent of hydride is measured by proton NMR and is about 1 molarpercent.

Step 2

Cool the reaction flask from step 1 to room temperature. Then add 26.5 gof triacontene (e.g., Gulftene 30+, commercially available from Chevron,a mixture of alkene materials having an alpha-olefin content greaterthan 60%, and an average chain length of about 36) and 400 mL toluene(dried with molecular sieves). Fill the reaction mixture with nitrogen.Heat to 75° C., measure IR of a solution aliquot, and add 50 μL of PC072(Platinum, 1,3-diethenyl-1,1,3,3-tetramethyldisoloxane complex) (time=0min). At 20 minutes add 50 μL of PC072 and measure IR. Continue to add50 μL every 20 minutes taking IR of aliquot until percent hydride (%H)reaches 25-30% of original (time=0 min.) hydride integration from IR (noless than 40 min. addition; nor more than 60 min. addition). When the %hydride reaches 25-30% add 50 mL of hexene and 50 μL of PC072 (quenchtime=0 min.). At 30 minutes add another 50 μL of PC072. Continuemonitoring by IR until the % hydride is below 10% of original hydrideintegration (normally 1 hour).

Procedure for Adding Antioxidant

From step 2, add in 3% Cyanox STDP, 0.6% Irganox 1010, 0.9% Mark 2112antioxidants based on amount of sealant (if assumed 241.3 g sealant:7.24 g STDP, 1.45 g 1010, and 2.17 g 2112). Heat (100° C.) and stiruntil mixed (1 hour). Pour into oven dish, dry in explosion proof oven(˜75° C.) overnight.

A small quantity of the material synthesized above is used to seal theends of the developer roll in the developer section of the printingcartridge. This sealing operation prevents the toner from leaking intothe transfer section of the cartridge. The material is inside thecartridge where it cannot be touched by the customer; it is not releasedduring the printing process.

To apply the material, the cartridge assembly person takes a smallamount of the material (about 40 mg) on the end of a tool that is like aflat screwdriver and places that amount of material on each end of thedeveloper roll and on the J-seal. The roll is then turned to distributethe material around the roll, forming a thin layer, sealing the ends ofthe roll and the J-seal to prevent toner from escaping.

What is claimed is:
 1. A toner cartridge comprising pliablepolyorganosiloxane sealant comprising structural units of the formulae:##STR9## wherein (i) each R is independently a C₁ -C₆ alkyl (ii) each R¹is independently selected from the group consisting of a C₂ -C₁₄ alkyland a C₁₅ -C₆₀ alkyl, with the proviso that from about 70% to about 100%of all R¹ groups are C₁₅ -C₆₀ alkyl, and (iii) x represents from about 0to about 99.5 mole percent, and y represents from about 0.5 to about100.0 mole percent of the silicone copolymer, based on total moles ofthe silicone copolymer.
 2. A toner cartridge according to claim 1wherein said silicone copolymer is a random copolymer and wherein x isfrom greater than about 98.5 to about 99.5 and y is from about 0.5 toless than about 1.5.
 3. A toner cartridge according to claim 2 whereinsaid silicone copolymer is terminated with groups having the formulae:##STR10## wherein each R² is independently a C₁ -C₆ alkyl or aryl group.4. A toner cartridge according to claim 3 wherein in said siliconecopolymer R is a methyl group.
 5. A toner cartridge according to claim 3wherein in said silicone copolymer R² is a methyl group.
 6. A tonercartridge according to claim 3 wherein said silicone copolymer has aweight average molecular weight of from about 10,000 to about 1,000,000.7. A toner cartridge according to claim 6 wherein said siliconecopolymer has a weight average molecular weight of from about 80,000 toabout 250,000.
 8. A toner cartridge according to claim 6 which includesa developer roll having from about 5 mg to about 100 mg of said siliconecopolymer as a sealant on each J-seal at each end of said developerroll.
 9. A toner cartridge according to claim 8 wherein about 40 mg ofsaid silicone copolymer is present on each J-seal at each end of saiddeveloper roll.
 10. A toner cartridge in accordance with claim 1 inwhich said R is methyl.
 11. A toner cartridge in accordance with claim 2in which said R is methyl.